1. Field of the Invention
The present invention relates to a clipping circuit for performing wave shaping on a signal fed thereto, and to an image processing device employing such a clipping circuit. The present invention relates particularly to a clipping circuit for clipping edge-enhanced image signals, and to an image processing device employing such a clipping circuit.
2. Description of the Prior Art
Conventionally, Laplacian processing is used to obtain satisfactory contrast and sharpness in a reproduced image by making the outline of a subject clear. Laplacian processing achieves edge enhancement by adding, to the image signals output from individual pixels to represent a subject of which the outline is to be targeted, signals representing edge components that are calculated by using Laplacian operator, which is a second-order differential operator. FIGS. 8A to 8C show how image signals undergo Laplacian processing. When image signals as shown in FIG. 8A are fed in, edge signals representing edge components as shown in FIG. 8B are calculated. Then, as shown in FIG. 8C, the edge components represented by those edge signals are superimposed on the image signals, so that edge-enhanced image signals are produced. In this way, it is possible to obtain enhanced sharpness and satisfactory contrast in a reproduced image.
As described above, by superimposing edge components represented by edge signals on image signals, it is possible to make changes in data values (i.e. changes in signal intensity) at edges sharper, and thereby obtain an edge-enhanced image. However, as FIG. 8C clearly shows, as a result of Laplacian processing, in the image signals that give the data values at edges, preshoots occur in low-data-value portions, and overshoots occur in high-data-value portions. This causes ringing at edges in the reproduced image, and thereby makes the reproduced image appear unnatural.